Noob has a problem with really simple OpenGL example

Being the very, very new noob that I am, I'm failing to get the basics functioning as I expect them to in OpenGL.

My simple (very simple) single source file windows program is shown below. In WinMain() during the while loop I'm mapping two textures to two quads.

I'm using "glVertex3f" and "glTexCoord3f" functions, so I'd expect the depths to be honoured. Yet texture #13 is always drawn in front of texture #14 despite its depth being -1.0 compared to texture #13's depth of -0.5.

If I swap the code blocks for texture #13 and texture #14 around, the Z-order changes, whereas I'd always expect to see texture #13 behind texture #14 regardless of the order of my code blocks. It's as if the z-buffer doesn't exist!